The nature and dynamics of bacterial genomes

Though generally small and gene rich, bacterial genomes are constantly subjected to both mutational and population-level processes that operate to increase amounts of functionless DNA. As a result, the coding potential of bacterial genomes can be substantially lower than originally predicted. Whereas only a single pseudogene was included in the original annotation of the bacterium Escherichia coli, we estimate that this genome harbors hundreds of inactivated and otherwise functionless genes. Such regions will never yield a detectable phenotype, but their identification is vital to efforts to elucidate the biological role of all the proteins within the cell.     

Ecology. The value of nature and the nature of value

Ecosystems are capital assets: When properly managed, they yield a flow of vital goods and services. Relative to other forms of capital, however, ecosystems are poorly understood, scarcely monitored, and--in many important cases--undergoing rapid degradation. The process of economic valuation could greatly improve stewardship. This potential is now being realized with innovative financial instruments and institutional arrangements.     

高校图书馆合并重组后的资产管理

对高校图书馆合并重组后资产清查过程中存在的问题进行探讨,并结合工作实践,提出了加强高校图书馆资产管理的措施。     

Homoeologous Heterozygosity and Recombination in the Fern Pteridium aquilinum

The bracken fern, Pteridium aquilinum, which can form completely homozygous zygotes in a single generation of self-fertilization, has a genetic system that allows the storage and release of genetic variability in spite of this homozygosity. Analysis of the distribution of electrophoretically demonstrable genetic markers demonstrates that this system is based on recombination between duplicated, unlinked loci.     

稻瘟病菌重组研究概要

稻瘟病菌变异机制极其复杂,有性重组和准性重组可能起着重要作用,但在田问植株上还未找到直接证据,并综述了这两种变异机制的研究进展。     

Paleomagnetism and the nature of the geodynamo

Records of direct observations of the earth's magnetic field cover less than a ten-millionth ofthe known lifetime of the field. Thus our knowledge of several geomagnetic phenomena, critical to our understanding of the geodynamo, must come firom the paleomagnetic record. A combination of substantial advances during the past decade or so both in dynamo theory (previously the domain of the mathematician) and in paleomagnetism (previously the domain of the geologist) has led to provocative models of the earth's magnetic field and a better understanding of the geodynamo.     

Recombination Events in the Bacterial Genus Nocardia

Genetic recombination was demonstrated in the bacterial genus Nocardia. The compatibility mechanism governing recombination differs from that of Escherichia coli and the streptomycetes. Mutants of N. erythropolis or N. canicruria, of homologous origin, were incompatible, but mutants of heterologous origin were compatible. Such a compatibility system is suggestive of classic heterothallism which up to now has not been known among the bacteria.     

行政调查瑕疵形态的分析研究

作为特殊行政行为的行政调查,其实施能对相对人权益产生较大影响。尽可能穷尽行政调查的瑕疵状态并予以深入分析,能够为行政调查的后续研究奠定理论前提,特别是能为行政调查救济制度的针对性设计提供参考依据。     

Farming and the fate of wild nature

World food demand is expected to more than double by 2050. Decisions about how to meet this challenge will have profound effects on wild species and habitats. We show that farming is already the greatest extinction threat to birds (the best known taxon), and its adverse impacts look set to increase, especially in developing countries. Two competing solutions have been proposed: wildlife-friendly farming (which boosts densities of wild populations on farmland but may decrease agricultural yields) and land sparing (which minimizes demand for farmland by increasing yield). We present a model that identifies how to resolve the trade-off between these approaches. This shows that the best type of farming for species persistence depends on the demand for agricultural products and on how the population densities of different species on farmland change with agricultural yield. Empirical data on such density-yield functions are sparse, but evidence from a range of taxa in developing countries suggests that high-yield farming may allow more species to persist.     

Molecular biological mechanisms of speciation

Growing recognition that much of the evolutionary history of eukaryotic genomes reflects the operation of turnover processes involving repetitive DNA sequences has led to the recent formulation of models describing speciation as a consequence of such turnover. These models are of three general kinds: those attributing hybrid infertility to the process of transposition, those attributing hybrid infertility to mispairing between chromosomes of divergent repetitive DNA composition, and those assuming that change in repetitive DNA's can reset coordinated gene regulation. These models are discussed with respect to the kinds of evidence needed for their corroboration and to their significance for questions related to macroevolutionary punctuated equilibria and genetic revolutions.     

On the nature of intelligence

Our concept of intelligence has been heavily influenced by the development of intelligence tests as screening devices in education and personnel selection. An alternative approach is to begin with a theory of the process of cognition and identify those aspects of individual mental performance that should be important on theoretical grounds. Three classes of performance have been identified. These deal with a person's choice of an internal representation for a problem, strategies for manipulating the representation, and abilities to execute elementary information processing steps required by the strategy.     

Lactate Dehydrogenase Isozymes: Dissociation and Recombination of Subunits

Lactate dehydrogenase from beef tissues may be resolved electrophoretically into five isozymes each of which is a tetramer. These tetramers can be dissociated into monomers by freezing in 1M sodium chloride. On thawing, reassociation into functional tetramers occurs. On the basis of charge and amino acid composition there are two kinds of monomers. Lactate dehydrogenase-1 contains one kind of monomer and lactate dehydrogenase-5 the other kind. A mixture of equal quantities of these two isozymes, after dissociation and reassociation, leads to the production of all five isozymes in the expected proportions of 1:4:6:4:1.